The present invention relates to techniques for attaching rigid conduits onto a solid block as, for example, the body of a valve. In particular, the invention relates to techniques for attaching refrigerant tubing to the block of a thermal expansion valve employed for controlling refrigerant flow in a closed system.
Heretofore, refrigerant tubes have been attached to the body or block of the thermal expansion valve, particularly in automotive air conditioning applications, by means of providing a flanged fitting on the end of the tube and valve block with the aid of a clamp bar and face sealing O-rings.
However, this form of attachment has proven to be troublesome, and due to strain on the tubes, subject to leakage. This is particularly the situation where the tubes are lengthy and subjected to vibration as in automotive air conditioning applications when the severe vibration in service causes the fastening means employed to secure the clamp plate on the tube flange to loosen and permits the connection to leak refrigerant.
Thus it has been desired to find a way or means of attaching rigid refrigerant conduit fittings to a solid block, such as the body of a thermal expansion valve in a manner which is low in cost to facilitate mass production, such as encountered in automotive air conditioning applications, and yet provide a reliable seal having a long service life.
Referring to FIG. 4, a known technique for installing a tube fitting on a thermal expansion valve is shown where a conduit 1 has a convolution or annular bulge in the tube formed thereon. The conduit in the known technique of FIG. 4 is inserted in a counterbore with an O-ring 4 provided therein which seals around the outer surface of the conduit. A circular flanged portion 3 formed on the valve block is then deformed with a tool over the convolution on the tube and retains the tube in position in the block.